Along with the rapid development of mobile communication industry, the contradiction between an increasing demand of the broadband wireless communication and limit spectrum resources become more and more obvious. On one hand, although such techniques as Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) have been adopted by a Long Term Evolution (LTE) system so as to improve a spectrum utilization rate, these techniques are not fundamental solutions to the shortage of spectrum resources. In addition, along with the rapid development of mobile communication services, telecom operators are being confronted with a more serious situation of spectrum resource shortage. On the other hand, the frequency spectra of some radio communication systems are used rarely in some time periods and at some regions. For example, for radio and television bands, due to the replacement of analogue transmission with digital transmission where the transmission capacity can be improved remarkably, the bands of many radio and television systems are in a vacant state for a long period of time, resulting in the waste of the valuable radio resources. Furthermore, it is also found that the frequency spectra of some other radio communication systems are not utilized fully.
In order to overcome the shortage of the spectrum resources, a Cognitive Radio (CR) technology has attracted more and more attention. In the CR technique, a smart radio communication system may acquire a vacant band available at a current position through a spectrum sensing technique, and use the vacant band opportunistically, so as to improve the spectrum utilization rate and alleviate the shortage of the spectrum resources. As to an existing spectrum sensing technique, an external environment may be sensed by an artificial intelligence system, and some operating parameters, such as transmission power, a carrier frequency and a modulation technique, may be modified in real time, so as to enable an internal state of the communication system to be adapted to a change in the statistical characteristics of a received radio signal, thereby to achieve the reliable communication at any time and any location, and effectively utilize the spectrum resources.
The entire cognition procedure is completed by the CR technique through a cognition cycle. As shown in FIG. 1, the entire cognition procedure includes three steps, i.e., a spectrum sensing step, a spectrum analysis step and a spectrum decision step. At the spectrum sensing step, a vacant spectrum may be detected by analyzing an inputted radio frequency (RF) stimulating signal. Whether or not the spectrum is being occupied may be determined by detecting whether or not a signal exists at a certain band using a certain signal detection algorithm, e.g., an energy detection algorithm or a matched filtering detection algorithm, so as to detect the vacant spectrum. At the spectrum analysis step, channel state information and channel capacity may be estimated in accordance with a result obtained from the spectrum sensing step and the analysis on the other ratio signals. At the spectrum decision step, a final spectrum usage decision may be acquired in accordance with the vacant spectrum resources obtained at the spectrum sensing step and a result obtained from the spectrum analysis step. This decision may include frequency point, i.e., a decision on spectrum allocation, bandwidth, transmission power, and modulation mode.
Due to the limited vacant spectrum resources, it is required to allocate the vacant frequency spectra for a plurality of communication nodes appropriately. In the related art, the vacant frequency spectra may be allocated using an intersystem spectrum allocation method and an intercell spectrum allocation method.
For the intersystem spectrum allocation method, there is interference between cells of different radio communication systems when these systems are in an operating state, so the frequency spectra may be allocated uniformly among the various radio communication systems so as to eliminate the intersystem/intercell interference.
For the intercell spectrum allocation method, the radio communication system is of a cellular structure, and a large region is covered by a plurality of cells, so as to achieve continuous coverage and unlimited communication. There is also interference among a plurality of cells of an identical radio communication system. Taking the macrocell communication as an example, there is the interference between the adjacent macrocells, and especially the communication of a user at an edge of a cell may be interfered with a user or a base station in an adjacent cell. Based on this, the intercell interference may be suppressed mainly by network planning, i.e., by setting appropriate parameters for cell radius, cell coverage and cell switching.
It is found by the inventor that there are at least the following defects in the prior art. For the intersystem spectrum allocation method as a static one, the spectra are allocated for radio services/systems in accordance with their demands, and the spectrum utilization rate thereof is relatively small. For the intercell spectrum allocation method, as also a static one, it is required to re-plan the network and adjust the parameters rigorously so as to adjust the spectrum resources for the cells in the network, so it will take a long period of time. Furthermore, the CR system is a system where the spectrum resources are used dynamically, and obviously, such static spectrum allocation method as the intersystem spectrum allocation method and the intercell spectrum allocation method cannot be adapted to the CR system.